Rotation molded bodies are widely used as large size molded articles, vessels, tanks and the like used in the industrial fields such as automobile, electricity, house building material, civil engineering, agriculture, horticulture, forestry, fishery and environmental applications and the like. As the production method thereof, there is mentioned, for example, a method in which, first, a polyolefin composition for rotation molded body containing a polyolefin and a processing stabilizer or the like is filled in a molding die in an amount corresponding to about the half of the die, the die is closed together with another half part, then, the molding die is heated in an oven while rotating the die around the axis, and after the composition is spread on the wall surface of the molding die, the molding die is cooled, or other methods.
Patent document 1 discloses that, as the above-described processing stabilizer, tris(2,4-di-t-butylphenyl)phosphite (Irgafos 168: registered trademark, manufactured by Ciba Specialty Chemicals) of the following formula:
is used as one of phosphorus-based antioxidants, in a polyolefin, and yellowing of the resultant rotation molded body is suppressed.    (Patent document 1) JP-A No. 2000-248075 (Example 1A and B [0111] to [0119])